What Does P0172 Mean on Your 2020 Nissan Murano?
When your 2020 Nissan Murano triggers a P0172 code, it means the engine control module has detected a rich fuel condition on Bank 1 of your 3.5-liter VQ35DD direct-injection V6. This engine uses both direct and port injection, and a rich condition means too much fuel is entering the combustion chambers relative to the amount of air. The ECM uses feedback from oxygen sensors and fuel trim data to manage the air-fuel ratio, and when it can no longer correct the imbalance, P0172 gets stored.
Symptoms You Might Notice
- Illuminated check engine light
- Noticeable drop in fuel economy
- Black or dark gray exhaust smoke
- Rough or uneven idle
- Sluggish acceleration or hesitation
- Strong gasoline smell from the tailpipe
Common Causes of P0172 on the 2020 Murano
The VQ35DD engine in your Murano has a dual-injection system that adds some unique considerations:
- Contaminated or Failing MAF Sensor — The mass airflow sensor sits in the intake tract and measures incoming air. Road grime, oil residue from aftermarket air filters, or general contamination can throw off its readings. This is the number one cause of P0172 on Nissan V6 engines.
- Leaking Direct Fuel Injectors — The VQ35DD uses high-pressure direct injectors that spray fuel directly into the combustion chamber. A leaking injector delivers fuel even when it shouldn't, creating an overly rich mixture.
- Faulty Oxygen Sensor (Bank 1 Sensor 1) — The upstream O2 sensor provides real-time feedback about exhaust gas composition. A sluggish sensor can mislead the ECM into adding too much fuel.
- High Fuel Pressure — A failing fuel pressure regulator or restricted fuel return line can push excessive fuel into the engine.
How to Diagnose the Problem
Follow these steps to narrow down the cause:
- Read fuel trim data — Connect a scan tool and check short-term and long-term fuel trims on Bank 1. Long-term fuel trim below -10% confirms the ECM is actively pulling fuel to compensate.
- Inspect and test the MAF sensor — At idle, the MAF sensor on the VQ35DD should read approximately 7-14 g/s. Readings significantly higher suggest contamination. Clean with MAF-specific spray and recheck.
- Monitor O2 sensor waveform — The Bank 1 upstream sensor should oscillate between 0.1V and 0.9V. A sensor stuck high (above 0.7V) indicates a rich reading.
- Check fuel pressure — The direct injection system operates at very high pressures (around 1,500-2,900 psi). Verify the high-pressure fuel pump and regulator are within spec using a compatible scan tool.
- Inspect for intake leaks or a stuck PCV valve — Check all vacuum hoses and the PCV system for proper operation.
Repair Options and Estimated Costs
- MAF sensor cleaning — $10-$30 (DIY with MAF cleaner spray)
- MAF sensor replacement — $130-$300 parts and labor
- Oxygen sensor replacement (Bank 1) — $200-$380 parts and labor
- Direct fuel injector replacement — $350-$750 (direct injectors cost more than port injectors)
- Fuel pressure regulator service — $150-$350 parts and labor
MAF sensor cleaning is the best first step since it costs almost nothing and solves the problem about 40% of the time. O2 sensor and injector work on the Murano is moderate difficulty for a DIY mechanic with the right tools.
Prevention Tips
- Replace the engine air filter on schedule — every 15,000-20,000 miles
- Avoid oiled aftermarket air filters, as excess oil can contaminate the MAF sensor
- Use Top Tier gasoline to keep direct injectors clean
- Address any check engine lights promptly to prevent secondary damage
- Follow Nissan's maintenance schedule for spark plugs and fuel system service